This invention generally relates to an improved lock rod clamping apparatus for detachably connecting a tool unit to a tool supporter, and is particularly concerned with such an apparatus having a shortened lock rod stroke.
Clamping mechanisms for detachably connecting a tool unit to a tool supporter are well known in the art. Such mechanisms are typically used in machining operations where the tool unit holds a cutting insert that is moved into and out of cutting engagement with a rotating metal workpiece. The clamping apparatus allows different tool units holding different cutting inserts to be quickly attached to and detached from the tool supporter which in turn is connected to a device that controls the movement of the tool unit with respect to the workpiece.
One of the most commercially successful clamping mechanisms includes a cylindrically-shaped canister member that is matable with the tubular end of a tool unit and which includes apertures for admitting locking elements into locking engagement with recesses present in the tool unit. The locking elements, which are typically spherical, are radially moved through the apertures in the canister member by means of a reciprocating lock rod having cam portions that engage the locking elements. Examples of such a clamping mechanism are disclosed in Erickson U.S. Pat. Nos. 4,708,040; 4,747,735; 4,836,068, and 4,932,295, each of which is assigned to Kennametal, Inc. located in Latrobe, Pa.
Such a clamping mechanism is illustrated in FIG. 6. Here, a side cross-sectional view of the distal end 62 of a canister member 39 is shown which includes an aperture 54a in the form of a cylindrical bore through the wall of the member 39. The inner diameter of the circular bore forming the aperture 54a closely approximates the outer diameter of the spherical locking element 57a. The lock rod 60 includes a cam portion 64a having a spherical depression 66 which tapers off into a ramp 68. When the spherical locking element 57a is seated in the depression 66, and the stop flange 70 of the lock rod 60 abuts annular wall 71, the spherical element 57a is in a non-locking position which would allow the tubular shank 16 of a tool unit 10 to be inserted into the annular recess 59 of the coupling member 43. However, when the lock rod 60 is moved to the right in the position illustrated, the ramp 68 of the cam portion 64a wedgingly engages and raises the spherical locking element 57a into the locking position. In such a position, the spherical locking element 57a will wedgingly and lockingly bear against an angled wall 30 of the tool unit 10.
While such a prior art locking mechanism has proven its capability of quickly, conveniently, and rigidly attaching a tool unit to a tool supporter, the applicant has observed that if the stroke of the lock rod could be shortened, the overall envelope of the clamping mechanism could likewise be shortened. Such a shortened tool envelope would facilitate machining operations by allowing the operator to more conveniently use the clamping mechanism without interference from surrounding tools or other obstructions. Even more importantly, a shorter lock rod stroke would reduce the stresses applied to the spring package used to pull the lock rod from an unlocked to a locked position. Such a spring package may take the form of a hydraulic cylinder connected to the lock rod, or a stack of resiliently compressed Bellville washers slidably mounted around the proximal end of the canister member. Where stacked Bellville washers are used, a shorter lock rod stroke would allow the use of a shorter stack of washers while increasing their useful life span. Alternatively, a regular size spring package of such washers could be used in combination with a shorter lock rod stroke to produce a clamping mechanism that gripped a tool unit with a greater holding force, which in turn would increase the tool rigidity and hence the accuracy of the machining operations performed by the tool unit.
Clearly, it would be highly advantageous if a way could be found to shorten the stroke of the lock rod used in such clamping mechanisms without sacrificing the convenience, speed, and rigidity that such a mechanism offers in attaching and detaching tool units to a tool supporter. Ideally, such a stroke-shortening solution should require only a minimal amount of modification to the shapes of existing parts so that a conventional clamping mechanism of the type previously described could easily be converted into an improved clamping mechanism with a minimum amount of component redesign and machining.